Add Figma designs for chat using the new Nebari design system

[smeragoel]

Summary

The chat application is functional, but there are currently no design files for it in Figma. The chat today uses its own independent/ad-hoc design language that is not aligned with the rest of the Nebari product.

This issue tracks creating the first set of Figma designs for chat, built on top of the new Nebari design system.

Background

• The chat frontend already exists and works.
• No Figma source of truth exists for any chat screen or component.
• The chat's current visual design is independent and not consistent with the broader Nebari UI.
• A new Nebari design system (tokens + components) now exists in Figma and should be the foundation for chat going forward.

Goal

Create Figma designs for chat that are composed from the new design system components (rather than bespoke chat-only styling), so chat becomes visually consistent with the rest of Nebari and has a maintainable design source of truth.

Scope

• Set up a Figma file (or page) for chat designs.
• Design chat screens using the new design system's tokens and components.
• Identify any chat-specific patterns that the design system does not yet cover, and flag them as candidates for new shared components vs. one-off chat components.

Out of scope

• Implementing the new design in code (this issue covers the design artifacts only).

Notes

The chat itself is unchanged by this work — this is about establishing the design foundation and aligning chat with the new design system.